The TARwhat?
by Omegalomaniac
Summary: When a body is found outside the NCIS Headquarters, it's assumed to be a warning. What if it's not; what if someone - or something - is trying to infiltrate NCIS? And who is this strange man claiming to know Ducky? Doctor Who/NCIS crossover.
1. Prologue

**Disclaimer:** I don't own NCIS or Doctor Who, unfortunately...

**A/N: **Set after series 4 of Doctor Who and sometime in Season 5 of NCIS.

* * *

**Prologue**

"We'd make an awesome superhero team." Special Agent Anthony DiNozzo grinned, leaning his head back against his hands as he absent-mindedly tipped his chair back.

"How'd you figure that out, then?" Timothy McGee glanced at his co-worker over the top of his book.

"Well, we have Ziva… Ninjawoman!"

"I am not a ninja, Tony," the Mossad agent sighed.

Tony continued as if he hadn't heard her. "Probieman, the computer geek. And, of course, me, the handsome one that always ends up saving the day. Just haven't thought of a heroic enough name for me yet."

"So, what about Gibbs?" McGee couldn't help it, he was curious.

"What about Gibbs?" The person in question strode down the steps, holding a large polystyrene Caf-Pow! cup, and walked straight past the three of them towards the elevator. "Coming?"

"Uh, nothing, boss." McGee jumped to his feet, noticing Tony and Ziva doing the exact same. Hurriedly, he shoved his book into the drawer in his desk and picked up his equipment before following his boss and co-workers into the elevator.

"Where are we going, boss?" Tony enquired.

"You'll see," was all Gibbs gave as an answer, leaving the elevator in silence as it descended down towards the ground floor. He was still silent as he led Tony, Ziva and McGee out of the building and into the bright sunlight.

He didn't need to speak. For, lying there on the slightly-pink, bricked walkway in front of the Naval Criminal Investigative Service Headquarters was a body, surrounded by officers.

"Well, someone sure wanted our attention," Tony murmured.

"But for what purpose?" a voice behind them spoke. "A rather morbid way of doing so, don't you think?"

"And how did she get here?" McGee followed on from the medical examiner's question.

"As far as we can tell, she just appeared here." The oldest and seemingly highest ranked of the officers shrugged as the rest left the scene. "No ID, no witnesses, no nothing."

"'No nothing' implies the presence of something." Dr Donald 'Ducky' Mallard knelt down by the body, continuing a minute or so later with, "Body temperature is ninety-five degrees, rigor mortis is barely setting in. This woman hasn't been dead long. An hour or so, perhaps."

"To manage to plant her here would have needed planning," Ziva noted, snapping a picture of the corpse's tightly fisted hand, in which was a scrunched up piece of paper.

"Cause of death?"

"No obvious signs of trauma, but something appears to have burned through her top, here." Ducky gestured at the corpse. "For anything more definite, you'll have to wait until we get her inside."

"Ziva, DiNozzo, photos. McGee, check the security tapes and find out who the hell she is!" Gibbs ordered, striding back towards the building as his team unanimously cried in reply, "On it, boss!"

* * *

"Abby ran our Jane Doe through CODIS. No match. No-one with her description has been reported missing recently, either." Tony stopped his pacing and stood directly in front of the plasma screen to stare at the crime scene photo displayed.

"There's nothing on the security tapes, boss. They've been wiped. Completely. Whoever did this knew what they were doing. I'm trying to find the hacker now…" McGee stared helplessly at his keyboard.

"And, the piece of paper we found in her hand seems to be in some sort of code." Ziva sighed.

"So, basically, we've got nothing," Gibbs summed up the team's findings, reaching for his phone as it began to ring. "Yeah, Duck?"

"You may want to see this, Jethro."

Without answering, Gibbs shut the phone with a snap, ending the short call, before heading off towards the autopsy room.

* * *

"Have you ever played laser tag, Doctor?" Jimmy Palmer asked as he examined the odd burn mark on the corpse.

"Ah, no, Mr Palmer. Not really my type of game nowadays. I don't believe that it was her type of game either, was it, my dear?" he addressed the body.

"Cricket," Gibbs answered Palmer's next question before he had time to speak it. "What killed her, Duck?"

"See this burn mark, here? This poor woman was hit with a beam of intense heat. Once it managed to burn through her skin, it boiled her insides instantaneously. My guess would be some sort of laser. That makes my earlier estimate of time of death void, I'm afraid. However," Ducky picked up a jar filled with what appeared to be purple sludge, "I found this in the remains of what was probably her stomach. I've sent a sample to Abigail for testing, but it's nothing I've seen before. I only hope she can give you more than I can."

* * *

"I know your game. You're trying to trick me." Abby glared at the computer screen. "No machine can fool me! I'll find your secrets, you can bet on it!"

"Any luck, Abs?"

"Oh! Gibbs!" Abby spun around and gave Gibbs a quick hug before relieving him of the Caf-Pow! in his hand. Three noisy slurps later, she placed the cup on the desk next to her and returned to glaring at the screen. "No. I analysed that purple sludge stuff that Ducky sent me and I didn't recognise the chemical composition at all. I'm running it through the computer now."

Right on cue, the screen changed from showing a list of scrolling chemical symbols to two flashing, bold words. 'Compound Unknown.'

"Ha! You think you've got the better of me…" Abby growled, reaching for the Caf-Pow! and tapping a few keys on her keyboard. "Most of the compound doesn't even seem to be in the system. That's odd. The only thing it can recognise is… Water."

"Water?"

"I'll try running this manually. It may take a while…" Abby trailed off as Gibbs produced another Caf-Pow! from behind his back. "A short while," she quickly corrected herself.

* * *

"Got anything?"

"Nothing. We have nothing," Tony replied.

"Why would someone get our attention and then not give us any clue?" Ziva mused.

"Well, there's the note," McGee pondered, tapping his keyboard to bring a scan of the note up on the plasma screen.

Ziva sighed. "It's not in any known language or code and we cannot translate it."

"Ohh… That may be a job for me."

In unison, Gibbs, Tony, Ziva and McGee spun around to see the newcomer who had spoken. He was tall, with hair that seemed to have a mind of its own, and was wearing a brown pinstripe suit. He had his hands shoved in his trouser pockets and didn't at all seem perturbed about standing in the middle of the squad room without a visitor's pass hanging around his neck.

Within a manner of seconds, four guns were pointing at him.

"Well, that's not a very nice welcome."

"How did you get in here?" Gibbs barked.

The man made a vague gesture towards the elevator. "Walked in."

"That is impossible." Ziva narrowed her eyes. "You would have been stopped by security."

Four safety catches were clicked off as the man reached into his pocket and pulled out a battered brown wallet. "Look," he said, showing the paper inside to them.

"You're from the British Embassy?" Tony lowered his gun. "You still should have got a pass."

"That paper is blank," Ziva argued.

Tony glanced at her, puzzled. "Ziva, it clearly isn't."

"No. You just want it to not be blank. You expect it to not be. It is all in the mind." If she had not have been holding her gun steady, Ziva would have tapped the side of her head to emphasize her words.

McGee was crossing and uncrossing his eyes and squinting at the paper. "If I do this, it has writing on it. If I do this, it's blank."

"Oh, come on! I can't really be imagining words!" Tony looked at Gibbs for support.

"She's right, DiNozzo. It's blank."

"Ah, well. Worth a try." The man returned the wallet to his pocket. "This _is_ NCIS, isn't it? I'm looking for Doctor Donald Mallard."

By now, officers had gathered around the squad room, sealing off any means of escape for the man. Gibbs gestured at two of them and they grabbed his arms tightly. Gibbs opened his mouth to speak, but was cut off by a voice from the top of the stairs.

"Take him to interrogation," Director Jenny Shepard ordered. "Jethro, my office. Now."

* * *

"What was that about?" Jenny watched Gibbs closely as he closed the door behind him and walked over to stand right in front of her desk.

"I have no idea," Gibbs confessed.

Jenny sighed, knowing that he wouldn't admit that lightly. "I've sent Ziva to interrogate him. Any leads on this Jane Doe?"

"Nothing."

"I have a funny feeling that this is a warning, Jethro." Jenny reached over to press the speaker button as the phone on the desk buzzed. "Yes?"

"Agent DiNozzo, Director," the woman on the other end said.

"Let him in," Jenny replied, pushing a stack of papers to the side of her desk.

"Uh, hey, boss, Director." Tony closed the door behind him. "Ziva's getting nothing. This guy just wants to talk to Ducky. Says he knows something about the case."

"Then get Doctor Mallard in there. I need something definite on this before I talk to SecNav."

* * *

"Ducky!"

"Back again so soon, Jethro?" Ducky turned away from the body drawer and towards the man who had just entered the room.

"You've got a visitor."

"A visitor?" Ducky sounded surprised.

"Yup. Says he knows you. More importantly, says he knows something about her." Gibbs gestured towards the drawer. "Ziva's with him, but he's not saying anything."

"I would not say that!" Ziva marched into the room, glaring at everything and nothing. "I have never heard anyone talk so much and yet say so little!"

"Well then, I should not be so discourteous as to leave this visitor waiting."


	2. Chapter 1

**Chapter 1**

"Doctor Donald Mallard!" The man grinned as Ducky entered the interrogation room and sat down opposite him. "Hello!"

"You asked to see me?"

"Ah. Yes." The man leant back in his chair and awkwardly scratched the back of his neck with his right hand. "I suppose I've changed a bit since we last met."

"I apologise if I don't remember you." Ducky frowned, sure that he had never before met the man sitting opposite him.

"Nineteen fifties. Edinburgh University. Cricket? I was blond," the man helpfully explained.

On the other side of the one-way glass, Ziva hissed to Tony, "Nineteen fifties? He would not have been alive then."

"Maybe he has a very good plastic surgeon," Tony suggested, earning a pained sigh from Ziva.

"Doctor?" Ducky ventured hesitantly after a minute's thought.

"Hello!" The man - the Doctor - grinned again.

Ziva and Tony glanced in surprise at each other. A moment later, Gibbs joined them by the glass with yet another caffeine-filled cup.

"What are you doing here?" Ducky enquired.

"There's this… Thing." Removing his right hand from the back of his neck, the Doctor wafted it around in front of him in what was probably an attempt to give an impression of the 'thing'. "I've been tracking it for a while and it appears to have ended up here."

"In NCIS?"

"It's been looking for something. It could already be inside." The Doctor paused, then leant forward and rested his elbows on the table. "Did you find anything odd inside the body that was outside earlier?"

"There was some, ah, purple sludge. It's with our forensic specialist now."

The Doctor turned his head towards the one-way glass. "Can I see this purple sludge?"

"Get him a pass, DiNozzo," Gibbs ordered before pushing open the door of the interrogation room and beckoning Ducky out. "Do you trust him?" he whispered as he shut the door firmly behind them.

"Yes," Ducky affirmed.

Gibbs stared at Ducky for a few moments longer, then inclined his head slightly in acceptance and opened the door once again. "Come on then," he said to the Doctor.

The Doctor grinned. "Brilliant."

* * *

"Five. Four. Three. Two. One." Abby grinned as she finished the countdown and twisted around from the computers to face the space that had been behind her, determined not to be sneaked up on again. She blinked twice, then the grin slid from her face as she realised there was no-one there. Turning back to the computers, she quietly muttered, "Oh."

A second later, she jumped in surprise as she felt fingers gently tapping on her right shoulder.

Turning once again, she glared at the culprit. "You're late."

"Sorry, had to get someone," Gibbs replied. "I'm assuming you have something for me."

Abby craned her head around Gibbs, even more certain than before with her theory that he was slightly psychic, to look at the two men standing behind him. Ducky smiled at her, whilst the other man, who had a visitor's pass haphazardly strung around his neck, was looking around the room as if he was barely managing to stop himself from closely examining everything in the lab.

"No, I don't have anything," she said. "Well, I don't have anything apart from the fact that I don't have anything, which is really strange in itself. That's why I wanted to talk to you. This stuff, it's not normal, it's like it's…" she trailed off, unsure of what to say.

"Alien?" the man suggested, slightly surprising Abby with his British accent.

"Well… Yeah," she admitted, having no other sensible way to describe it.

"Abs, this is the Doctor." Gibbs gestured towards the man, who brought his gaze away from the mass spectrometer to look at Abby. "He's here to help with the case."

"Yup." The Doctor grinned at her. "So, purple sludge?"

Abby grinned back and plucked a test tube out of the rack nestled between the two monitors. "I've done the usual tests, and then tested it again - anything else could take days, but I was going to start-" she broke off as the Doctor snatched the test tube from her hand and pulled a silver cylinder out of his jacket pocket. He pointed the cylinder at the tube, pressing a button which made it buzz loudly and emit a glowing blue light from the end. He slowly moved it around the tube, which seemed to increase the pitch of the buzzing-slash-whining sound coming from it.

"Hmm." He peered closely at the side of the cylinder and handed the test tube back to Abby.

"What's that?" she asked curiously, placing the test tube back in the rack.

"Sonic screwdriver," he replied, pointing it towards the monitors. With another quick buzz, information began to rapidly fill the screens. Abby recognised part of it as a chemical composition, though it was incredibly complicated and most of the symbols didn't appear to be in English.

"Doesn't look like a screwdriver." Gibbs stared suspiciously at the cylinder.

The Doctor looked down at the object in his hand, muttering to himself, "Why does everyone question the screwdriver?" before facing the information on the screens. "This," he said, "is what I was looking for."

"I thought you were tracking someone?" Ducky asked.

"Some_thing_," the Doctor replied, pushing a pair of glasses onto his face and peering more intently at the strange symbols. The sonic screwdriver disappeared back into his jacket pocket.

"You were tracking purple goo?" Abby glanced at the test tube containing the sample that the Doctor had just examined.

"I didn't _know_ it was purple goo. I just knew it was looking for something. Something here in NCIS." Upon seeing the sceptical faces of Abby, Gibbs and Ducky, he added, "It's alive."

"Alive," Gibbs echoed him with a sigh. "Duck-"

"Well, not that," the Doctor hastily interrupted, gesturing towards the completely inanimate sample in the test tube. "That's dead. It was cut off from the main body." Upon saying this, he frowned, a distracted look on his face. "Where _is _the rest of it?"

"I gave it to Mr Palmer to take down to evidence," Ducky said.

"Oh. _Oh_." The Doctor stared at him - or, rather, he stared at the space which Ducky simply happened to occupy at that moment in time - as if suddenly everything became clear.

There was a slight pause as everyone else failed to understand what was so important and obvious.

"If you're looking for something in NCIS, where would you go - where's the most likely place for it to be?" the Doctor tried to explain.

"Evidence," Gibbs realised.


End file.
